Planarization is the process of increasing the flatness of semiconductor wafer surfaces using planarization techniques. Starting raw wafers for semiconductor device fabrication generally have a flat or planar surface into which a plurality of gaps or trenches is etched. As the wafer goes through the various steps of device fabrication, layers of different materials, shapes, and depths are deposited over the wafer surface through different growth and deposition techniques. At times, portions of these materials already deposited over the wafer need to be removed. This series of material growth, deposition, and removal steps decreases the flatness or planarity of the wafer surface.
Modern fabrication techniques that increase the number of layers applied to the wafer while decreasing the width of the etched lines or trenches may increase the likelihood of wafer non-planarity.
Typical coating formulations use a single solvent or a combination of solvents with similar boiling points. Generally, a coating formulation with a high boiling point solvent has a higher viscosity, and a coating formulation with a low boiling point solvent has a lower viscosity. While coating formulations with a high viscosity may be desirable for providing thicker coatings, such coatings may not adequately provide fill of gaps or trenches, in particular gaps or trenches having relatively high aspect ratios. Conversely, less viscous coating formulations typically provide adequate gap filling ability, but the lower viscosity typically results in thinner layers of the coating formed along the wafer surface.
Improvements in the foregoing are desired, wherein surface features of an underlying substrate may be completely filled with high solid content planarizing formulations.